Certain quaternary n-propargyl pyridinium salts



United States Patent 574,843 U.S. Cl. 260-295 7 Claims Int. Cl. C071131/34, 31/44; C23b /08 ABSTRACT OF THE DISCLOSURE In accordance withcertain of its aspects, this invention relates to novel pyridiniumcompounds having a cation of the structure iLoHz-oEcH wherein A and Bmay each be selected from the group consisting of hydrogen,carboxamido-CoNH- acetyl- COCH and carbomethoxy-COOCH and at least oneof A and B is other than hydrogen, and to the use of pyridiniumcompounds as primary brighteners in the electrodeposition of nickel.

This application is a divisional application of application Ser. No.347,046 filed Feb. 24, 1964 which has matured into U.S. Patent 3,296,103granted J an. 3, 1967.

This invention relates to electroplating nickel and more particularly tothe electrodeposition of bright nickel.

Nickel electrodeposits as plated from Watts, high chloride, fluoborate,etc. type baths are not bright when plated in thicknesses substantiallygreater than those of very thin strike" or flash coatings. Such depositsdo not increase in luster with increasing thickness but rather decreasein brightness until dull matte deposits are obtained. To obtain thickbright deposits from such baths, it is necessary to add certainadditives, commonly of organic nature, which assist in producing highlylustrous deposits with good rate of brightening. It is a commoncharacteristic of such so-called bright nickel plating baths that thedeposits tend to increase in luster with increasing thickness. Aparticular advantage of these bright nickel baths is that brightdeposits can be obtained on basis metals which have not been polished orwhich do not have a high starting luster, within reasonablespecification thicknesses of nickel. Other concomitant advantages suchas leveling or the ability of the deposits to fill in pores, scratches,or other superficial defects of the basis metal, may also be obtained.

Addition agents useful as brighteners in nickel plating baths aregenerally divided into two classes on the basis of their predominantfunction. Primary brighteners are materials used in very low orrelatively low concentration, typically 0.002-0.2 g./l., which bythemselves may or may not produce visible brightening action. Thoseprimary brighteners which may exhibit some brightening eiiects when usedalone generally also produce deleterious side effects such as reducedcathode efficiency, poor deposit color, deposit brittleness andexfoliation, very narrow bright plate range, or failure to plate at allon low current density areas. Secondary brighteners are materials whichare ordinarily used in combination with primary brighteners but inappreciably higher concentration than that of the primary brighteners,typically 1 g./l. to 30 g./l. These materials, by themselves, mayproduce some brightening or grain-refining eifects, but the deposits arenot usually mirror bright and the rate of brightening is usuallyinadequate.

Ideally, when primary and secondary brighteners of properly chosen andcompatible nature are combined it is possible to obtain, over a widecurrent density range, ductile, leveled deposits which exhibit a goodrate of brightening. The rate of brightening and leveling may vary indegree depending on the particular cooperating additives chosen andtheir actual and relative concentrations. A high degree of rate ofbrightening and leveling is generally desirable, particularly wheremaximum luster is desired with minimum nickel thicknesses. Theconcentrations of the secondary brighteners may usually vary withinfairly wide limits. The concentrations of the primary brighteners mustusually be maintained within fairly narrow limits in order to maintaindesirable properties including good ductility, adequate coverage overlow current density areas, etc. Any bright nickel system which can berendered more tolerant to fluctuations in primary brightenerconcentrations will have obvious advantages, particularly since the lowconcentration of primary brighteners and the intrinsic chemical natureof some make strict control by chemical analysis difiicult. A primarybrightener which can be used over a wide range of concentration is ofgreat value in bright nickel plating.

It is an object of this invention to provide improved nickel plate byuse of a new class of superior primary brighteners. It is a furtherobject of this invention to provide an efiicient process forelectrodepositing bright and smooth nickel deposits. Another object ofthis invention is to provide bath compositions for nickel plating fromwhich bright nickel electrodeposits are obtained. Other objects of thisinvention may be apparent to those skilled in the art on inspection ofthe following description.

In accordance with certain of its aspects, the process of this inventioncomprises electrodepositing nickel from an aqueous nickel electroplatingbath containing a secondary brightener and, as a primary brightener, acompound having a cation of the structure ILOHZ-CECH wherein A and B mayeach be selected from the group consisting of hydrogen, carboxamido-CONHacetyl- COCH and carbomethoxy-COOCH and at least one of A and B is otherthan hydrogen.

Typical compounds of this class which may be effective as primarybrighteners are the following:

TABLE I (A) 3-carboxamido N-propargyl pyridinium bromide (B) 3-acetylN-propargyl pyridinium bromide (C) 3-carbomethoxy N-propargyl pyridiniumbromide (D) 4-carboxamido N-propargyl pyridinium bromide (E) 4-acetylN-propargyl pyridinium bromide (F) 4-carbomethoxy Npropargyl pyridiniumbromide The novel class of primary brighteners of this invention whenused in combination with (a) suitable secondary brighteners or (b)secondary and secondary auxiliary brighteners, may give brilliant,nickel deposits which have excellent ductility, good low current densitycoverage and luster, good rate of brightening, and good levelingcharacteristics. It is a particular feature of this invention that thepreferred novel primary brighteners may be used over a wide range ofconcentation with attainment of good low current density coverage andductility of the deposits.

Another outstanding advantage is that these novel primary brightenerscan withstand long electrolysis without build-up in the nickel platingbath of harmful decomposition products. Prior art nickel platingtechniques may include the use of a number of acetylenically quaternizednitrogen heterocyclic compounds as primary brighteners; but they eitherproduce inadequately lustrous deposits or are difficult to synthesize inhigh purity and yield; they have limited compatibility with the morecommonly used additives. The compounds of this invention, including the3- and 4-substituted propargyl pyridinium quaternaries, do not havethese defects and in addition exhibit low rates of consumption. The 3-and 4-substituent groups of this invention are specifically chosen.Other groups in these positions either may be the quaternaries difficultor impossible to synthesize or result in compounds ineffective asprimary brighteners.

The primary brighteners of this invention may be used in concentrationsof 0.005 g./l. to 0.10 g./ 1., the particular concentration chosendepending on the particular t pes and concentration of secondary andsecondary auxiliary brighteners used, and also on such factors as theconcentrations of nickel sulfate, nickel chloride, and boric acid;operating conditions with respect to temperature and degree ofagitation; degree of luster, rate of brightening and leveling desired;and the finish of the basis metal. It is preferred to use between 0.01g./l. and 0.05 g./l.

Secondary brighteners (typically present in amount of 1 g./l. to 75g./l., and preferably 1 g./l. to 20 g./l.) which are useful incombination with the primary brighteners, are generally aromaticsulfonates, sulfonamides or sulfimides which may include suchsubstituted aromatic compounds as 1,3,6-naphthalene trisulfonate, sodiumor potassium salts of saccharin, sodium or potassium salts oforthosulfo-benzaldehyde, benzene sulfonamide, benzene monosulfonate,etc. For use in high chloride type nickel plating baths, a preferredsecondary brightener may be a sodium or potassium salt of sulfonateddibenzothiophene dioxide, prepared by sulfonating diphenyl with fumingsulfuric acid (20% oleum) for about 2 hours, isolating the reactionproduct, and neutralizing. The predominant reaction product is believedto be the compound containing three sulfonic acid groups, together withsome monoand disubstituted components. The secondary brighteners aregenerally characterized by having at least one sulfone or sulfonic acidgroup attached to a nuclear carbon of a homocyclic aromatic ring.

Auxiliary secondary brighteners such as sodium-2- propene-l-sulfonate;sodium-3-ch1oro-2-butene-1 sulfonate; mixed isomer ofsodium-Z-butene-2-hydroxy-l-sulfomate andsodium-2-butene-1-hydroxy-2-sulfonate, prepared by reacting butadienemonoxide with sodium sulfite; or phenyl propiolamide may be used inconjunction with the secondary brightener or brighteners.

Conventional baths and processes for electroplating bright nickel aredescribed in Principles of Electroplating and Electroforming, Blum andHogaboom, pages 362-381, revised third edition, 1949, McGraw-Hill BookCo., Inc., New York; and in Modern Electroplating, edited by A. G. Gray,The Electrochemical Society, 1953, pages 299-355. The control andoperating conditions, including the concentration of the bathingredients, pH, temperature, cathode current density, etc., of theseconventional baths are generally applicable to the present invention.Practically all baths for electroplating bright nickel contain nickelsulfate; a chloride, usually nickel chloride; a buffering agent, usuallyboric acid; and a wetting agent, e.g. sodium lauryl sulfate, sodiumlauryl ether sulfate, or sodium 7-ethyl-2-methyl-4-undecanol sulfate.Such baths include the Well-known Watts bath and the high chloride bath.Other baths may contain, as the source of the nickel, a combination ofnickel fluoborate with nickel sulfate and nickel chloride, or acombination of nickel fluoborate with nickel chloride. TypicalWatts-type baths and high chloride baths are noted in Tables II and III.

TABLE II.WATTS-TYPE BATHS Nickel sulfate 200 g./l. to 400 g./l. Nickelchloride 30 -g./l. to 75 g./l. Boric acid 30 g./l. to 50 g./l.Temperature 38 C. to 65 C. Agitation Mechanical and/or air or solutionpumping, etc. pH 2.5 to 4.5 electrometric. TABLE III-HIGH CHLORIDE BATHSNickel chloride g./l. to 300 g./l. Nickel sulfate 40 g./l. to 150 g./l.Boric acid 30 g./l. to 50 g./l. Temperature 38 C. to 65 C. AgitationMechanical and/or air or solution pumping, etc. pH 2.5 to 4.5electrometric.

Best plating results are usually achieved in the electrodepositionprocess when there is used a method of preventing the thin filmimmediately adjacent to the cathode from becoming depleted in cationcontent. This is desirably accomplished by agitation, such as by airagitation, solution pumping, moving cathode rod, etc.

For the purpose of giving those skilled in the art a betterunderstanding of the invention, illustrative examples are given. In eachof the examples, an aqueous acidic nickel-containing bath was made upwith the specified components. Electrodeposition of nickel was carriedout by passing electric current through an electric circuit comprising anickel anode an a sheet metal cathode, both immersed in the bath. Thebaths were agitated, usually by a moving cathode. Bright electrodepositswere obtained in all the tests included herein as examples.

In examples 1 through 14 inclusive, the following standard bath was usedas a base solution:

G./l. Nickel sulfate 300 Nickel chloride 60 Boric acid 45 Sodium laurylsulfate 0.25

The primary brighteners are identified from Table I, supra. Thesecondary brighteners which are used in the following examples as notedin Table IV infra, include:

TABLE IV.SECONDARY BRIGHTENERS The auxiliary secondary brighteners whichare used in the following examples as noted in Table V infra include:

TABLE V.-AUXILIARY SECONDARY BRIGHTENERS (K)sodium-3-chloro-2-butene-l-sulfonate (L) sodium allyl sulfonate In thefollowing examples a.s.d. signifies amperes per square decimeter.

TABLE VI Example No. Additive Amount, g./l. CD a.s.d. Temp, 0.

G 2. 0 K 3. 0 3 C 0.020 4 60 G 2. 0 K 3.0 4 D 0. 030 4 60 G 4. 0 K 4.0 5E 0.020 4 60 G 2. 0 K 3. 0 6 F 0. 020 5 50 G 2. 0 K 3. 0 7 A 0.030 5 60H 4. 0 K 4. 0 8 B 0. 030 4 60 H 4. 0 K 3. 0 9 B 0. 030 6 55 H 2. 0 K 4.0 10 E 0.020 4 60 G 4. 0 L 2. 0 11 E 0. 030 5 60 I 2. 0 L 2.0 12 A 0.0204 50 J 4. 0 K 3. 0 13 E 0.020 5 60 G 2. 0 K 3. 0 14 A 0. 020 4 55 InExamples 15-18 inclusive, the following standard The foregoing examplesillustrate specific baths and processes. It is understood that thecompositions and conditions may be varied. Although the potassium andsodium salts were most often used and are preferred, they may bepartially or completely replaced by such other salts as nickel,magnesium, etc. salts.

The nickel electrodeposits obtained from baths utilizing the novelbrightener combination are advantageous in that mirror-bright lustrouselectrodeposits having a high degree of ductility are obtained over awide range of cathode current densities. The bright nickelelectrodeposits are preferably plated on a copper or copper alloy basismetal. However, they may be electrodeposited directly on such metals asiron, steel, etc.

The novel primary brighteners of this invention may be prepared by thefollowing reaction:

Typical reactants which may be employed in the process of this inventionmay include:

3-carboxamido pyridine (nicotinamide) 3-carbomethoxy pyridine (methylnicotiuate) 3-acetyl pyridine Typical reactants which may be employed inthe process of this invention may include:

4-carboxamido pyridine (isonicotinamide) 4-carbomethoxy pyridine (methylisonicotinate) 4-acetyl pyridine Typical reactants HCEC--CH2X which maybe employed include those wherein X may be halogen. Most preferredbecause of ease of reaction and availability may be propargyl bromide,HCEC-CHzBl'.

It will be apparent to those skilled in the art that inertly substitutedreactants may be employed.

The reaction of the heterocyclic compound and the acetylenic halide maytypically be effected under mild conditions, preferably in the presenceof solvent. The reaction may occur readily in high yield typically atroom temperature with slight warming usually occurring at the beginningof the reaction. The product generally may be a well-defined crystallinesolid which may be recovered from the reaction system as by filtrationfollowed by washing with appropriate solvent such as acetone.Recrystallization is generally unnecessary and the product may be easilyair-dried.

The reaction may be carried out in the presence of inert solventsincluding preferably acetone, dimethylformamide, or mixtures thereof.

Carrying out the reaction may include dissolving one mole of theheterocyclic compound in an excess of solvent sufficient to dissolve thecompound. Typically the solvent may be present in amount of 3-4 timesthe weight of the compound. To this mixture there may be added at leastone mole and preferably 1-1.5 moles of acetylenic halide, preferablypropargyl bromide. The mixture may be allowed to stand at roomtemperature for two hours to several days depending on the particularproduct being prepared.

Conversion of the novel compounds to other novel compounds in practiceof this invention may be effected by the reaction thereof with e.g.soluble silver salts of desired anions such as acetate, sulfate,perchlorate, methosulfate, etc. Typically this reaction may be elfectedin aqueous medium by mixing equivalent amounts of the reactants andfiltering 011 the insoluble silver halide, e.g.

CONH:

AgOOOCHa them-c5011 CONH;

AgBr Yuan-050E.

occur Preparation of the novel compounds of this invention may befurther illustrated by the following illustrative specific Examples19-21:

Example 19.-Synthesis of 3-carboxamido N-propargyl pyridinium bromide 35g. nicotinamide, 100 ml. dimethylformamide, and 25 ml. propargyl bromidewere allowed to stand at room temperature for 68 hours. The crystallineproduct was filtered 01f, washed with acetone and air-dried. Yield 68 g.(94% )M.P. 187190 C. (by melting point as determined in the Fisher-Johnsapparatus).

Example ZO-Synthesis of 3-carbomethoxy N-propargyl pyridinium bromide g.of methylnicotinate, 25 ml. dimethylformamide, and ml. propargyl bromidewere allowed to stand at room temperature for 3 hours. The crystallineproduct was filtered off, washed with acetone and air-dried. Yield 15.55g. (83%)-M.P. 135-136 C. (Fisher-Johns).

Example 21-Synthesis of 4-acetyl N-propargyl pyridinium bromide 10.8 g.4-acetylpyridine, 25 ml. dimethylformamide, and 10 ml. propargyl bromidewere allowed to stand at room temperature for 25.5 hours. To thereaction mixture m1. acetone were added and the crystalline product wasfiltered oif, washed with acetone and dried in a desiccator. Yield 18.1g. (85%)-M.P. (darkens C. melts with decomposition about 280 C.)(Fisher-Johns).

Although this invention has been illustrated by reference to specificexamples, numerous changes and modifications thereof which clearly fallwithin the scope of the invention will be apparent to those skilled inthe art.

I claim:

1. A compound of the formula References Cited UNITED STATES PATENTS9/1962 Heilling 204-49 FOREIGN PATENTS 1,066,068 5/1961 Germany.

HENRY R. JILES, Primary Examiner.

40 ALAN L. ROTMAN, Assistant Examiner.

US. Cl. X.R.

